diff --git a/.github/changelog/add-same-server-domain-move b/.github/changelog/add-same-server-domain-move
new file mode 100644
index 000000000..1b4b9fc40
--- /dev/null
+++ b/.github/changelog/add-same-server-domain-move
@@ -0,0 +1,4 @@
+Significance: major
+Type: added
+
+Support same-server domain migrations ⏩
diff --git a/activitypub.php b/activitypub.php
index 0a89fded8..5bec4e6d7 100644
--- a/activitypub.php
+++ b/activitypub.php
@@ -76,6 +76,7 @@ function plugin_init() {
 	\add_action( 'init', array( __NAMESPACE__ . '\Mailer', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Mention', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Migration', 'init' ), 1 );
+	\add_action( 'init', array( __NAMESPACE__ . '\Move', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Options', 'init' ) );
 	\add_action( 'init', array( __NAMESPACE__ . '\Scheduler', 'init' ) );
 
diff --git a/includes/class-activitypub.php b/includes/class-activitypub.php
index 902050f01..1bf61988f 100644
--- a/includes/class-activitypub.php
+++ b/includes/class-activitypub.php
@@ -762,6 +762,15 @@ public static function register_user_meta() {
 			)
 		);
 
+		\register_meta(
+			'user',
+			$blog_prefix . 'activitypub_old_host_data',
+			array(
+				'description' => 'Actor object for the user on the old host.',
+				'single'      => true,
+			)
+		);
+
 		\register_meta(
 			'user',
 			$blog_prefix . 'activitypub_moved_to',
diff --git a/includes/class-dispatcher.php b/includes/class-dispatcher.php
index 09198789f..b76f00d1c 100644
--- a/includes/class-dispatcher.php
+++ b/includes/class-dispatcher.php
@@ -209,6 +209,15 @@ private static function send_to_inboxes( $inboxes, $outbox_item_id ) {
 		$actor   = Outbox::get_actor( \get_post( $outbox_item_id ) );
 		$retries = array();
 
+		/**
+		 * Fires before sending an Activity to inboxes.
+		 *
+		 * @param string $json           The ActivityPub Activity JSON.
+		 * @param array  $inboxes        The inboxes to send to.
+		 * @param int    $outbox_item_id The Outbox item ID.
+		 */
+		\do_action( 'activitypub_pre_send_to_inboxes', $json, $inboxes, $outbox_item_id );
+
 		foreach ( $inboxes as $inbox ) {
 			$result = safe_remote_post( $inbox, $json, $actor->get__id() );
 
diff --git a/includes/class-move.php b/includes/class-move.php
index 5e0c1acb0..18e54ad4d 100644
--- a/includes/class-move.php
+++ b/includes/class-move.php
@@ -10,6 +10,8 @@
 use Activitypub\Activity\Actor;
 use Activitypub\Activity\Activity;
 use Activitypub\Collection\Actors;
+use Activitypub\Model\Blog;
+use Activitypub\Model\User;
 
 /**
  * ActivityPub (Account) Move Class
@@ -17,6 +19,33 @@
  * @author Matthias Pfefferle
  */
 class Move {
+
+	/**
+	 * Initialize the Move class.
+	 */
+	public static function init() {
+		/**
+		 * Filter to enable automatically moving Fediverse accounts when the domain changes.
+		 *
+		 * @param bool $domain_moves_enabled Whether domain moves are enabled.
+		 */
+		$domain_moves_enabled = apply_filters( 'activitypub_enable_primary_domain_moves', false );
+
+		if ( $domain_moves_enabled ) {
+			// Add the filter to change the domain.
+			\add_filter( 'update_option_home', array( self::class, 'change_domain' ), 10, 2 );
+
+			if ( get_option( 'activitypub_old_host' ) ) {
+				\add_action( 'activitypub_construct_model_actor', array( self::class, 'maybe_initiate_old_user' ) );
+				\add_action( 'activitypub_pre_send_to_inboxes', array( self::class, 'pre_send_to_inboxes' ) );
+
+				if ( ! is_user_type_disabled( 'blog' ) ) {
+					\add_filter( 'activitypub_pre_get_by_username', array( self::class, 'old_blog_username' ), 10, 2 );
+				}
+			}
+		}
+	}
+
 	/**
 	 * Move an ActivityPub account from one location to another.
 	 *
@@ -161,4 +190,124 @@ private static function update_blog_also_known_as( $from ) {
 
 		\update_option( 'activitypub_blog_user_also_known_as', $also_known_as );
 	}
+
+	/**
+	 * Change domain for all ActivityPub Actors.
+	 *
+	 * This method handles domain migration according to the ActivityPub Data Portability spec.
+	 * It stores the old host and calls Move::internally for each available profile.
+	 * It also caches the JSON representation of the old Actor for future lookups.
+	 *
+	 * @param string $from The old domain.
+	 * @param string $to   The new domain.
+	 *
+	 * @return array Array of results from Move::internally calls.
+	 */
+	public static function change_domain( $from, $to ) {
+		// Get all actors that need to be migrated.
+		$actors = Actors::get_all();
+
+		$results   = array();
+		$to_host   = \wp_parse_url( $to, \PHP_URL_HOST );
+		$from_host = \wp_parse_url( $from, \PHP_URL_HOST );
+
+		// Store the old host for future reference.
+		\update_option( 'activitypub_old_host', $from_host );
+
+		// Process each actor.
+		foreach ( $actors as $actor ) {
+			$actor_id = $actor->get_id();
+
+			// Replace the new host with the old host in the actor ID.
+			$old_actor_id = str_replace( $to_host, $from_host, $actor_id );
+
+			// Call Move::internally for this actor.
+			$result = self::internally( $old_actor_id, $actor_id );
+
+			if ( \is_wp_error( $result ) ) {
+				// Log the error and continue with the next actor.
+				Debug::write_log( 'Error moving actor: ' . $actor_id . ' - ' . $result->get_error_message() );
+				continue;
+			}
+
+			$json = str_replace( $to_host, $from_host, $actor->to_json() );
+
+			// Save the current actor data after migration.
+			if ( $actor instanceof Blog ) {
+				\update_option( 'activitypub_blog_user_old_host_data', $json, false );
+			} else {
+				\update_user_option( $actor->get__id(), 'activitypub_old_host_data', $json, false );
+			}
+
+			$results[] = array(
+				'actor'  => $actor_id,
+				'result' => $result,
+			);
+		}
+
+		return $results;
+	}
+
+	/**
+	 * Maybe initiate old user.
+	 *
+	 * This method checks if the current request domain matches the old host.
+	 * If it does, it retrieves the cached data for the user and populates the instance.
+	 *
+	 * @param Blog|User $instance The Blog or User instance to populate.
+	 */
+	public static function maybe_initiate_old_user( $instance ) {
+		if ( ! Query::get_instance()->is_old_host_request() ) {
+			return;
+		}
+
+		if ( $instance instanceof Blog ) {
+			$cached_data = \get_option( 'activitypub_blog_user_old_host_data' );
+		} elseif ( $instance instanceof User ) {
+			$cached_data = \get_user_option( 'activitypub_old_host_data', $instance->get__id() );
+		}
+
+		if ( ! empty( $cached_data ) ) {
+			$instance->from_json( $cached_data );
+		}
+	}
+
+	/**
+	 * Pre-send to inboxes.
+	 *
+	 * @param string $json The ActivityPub Activity JSON.
+	 */
+	public static function pre_send_to_inboxes( $json ) {
+		$json = json_decode( $json, true );
+
+		if ( 'Move' !== $json['type'] ) {
+			return;
+		}
+
+		if ( is_same_domain( $json['object'] ) ) {
+			return;
+		}
+
+		Query::get_instance()->set_old_host_request();
+	}
+
+	/**
+	 * Filter to return the old blog username.
+	 *
+	 * @param null   $pre      The pre-existing value.
+	 * @param string $username The username to check.
+	 *
+	 * @return Blog|null The old blog instance or null.
+	 */
+	public static function old_blog_username( $pre, $username ) {
+		$old_host = \get_option( 'activitypub_old_host' );
+
+		// Special case for Blog Actor on old host.
+		if ( $old_host === $username && Query::get_instance()->is_old_host_request() ) {
+			// Return a new Blog instance which will load the cached data in its constructor.
+			$pre = new Blog();
+		}
+
+		return $pre;
+	}
 }
diff --git a/includes/class-query.php b/includes/class-query.php
index d8bcc9fb2..d2200c0f4 100644
--- a/includes/class-query.php
+++ b/includes/class-query.php
@@ -48,6 +48,13 @@ class Query {
 	 */
 	private $is_activitypub_request;
 
+	/**
+	 * Whether the current request is from the old host.
+	 *
+	 * @var bool
+	 */
+	private $is_old_host_request;
+
 	/**
 	 * The constructor.
 	 */
@@ -305,4 +312,40 @@ public function is_activitypub_request() {
 
 		return false;
 	}
+
+	/**
+	 * Check if the current request is from the old host.
+	 *
+	 * @return bool True if the request is from the old host, false otherwise.
+	 */
+	public function is_old_host_request() {
+		if ( isset( $this->is_old_host_request ) ) {
+			return $this->is_old_host_request;
+		}
+
+		$old_host = \get_option( 'activitypub_old_host' );
+
+		if ( ! $old_host ) {
+			$this->is_old_host_request = false;
+			return false;
+		}
+
+		$request_host = isset( $_SERVER['HTTP_HOST'] ) ? \sanitize_text_field( \wp_unslash( $_SERVER['HTTP_HOST'] ) ) : '';
+		$referer_host = isset( $_SERVER['HTTP_REFERER'] ) ? \wp_parse_url( \sanitize_text_field( \wp_unslash( $_SERVER['HTTP_REFERER'] ) ), PHP_URL_HOST ) : '';
+
+		// Check if the domain matches either the request domain or referer.
+		$check                     = $old_host === $request_host || $old_host === $referer_host;
+		$this->is_old_host_request = $check;
+
+		return $check;
+	}
+
+	/**
+	 * Fake an old host request.
+	 *
+	 * @param bool $state Optional. The state to set. Default true.
+	 */
+	public function set_old_host_request( $state = true ) {
+		$this->is_old_host_request = $state;
+	}
 }
diff --git a/includes/class-signature.php b/includes/class-signature.php
index 89aa52114..98cfec229 100644
--- a/includes/class-signature.php
+++ b/includes/class-signature.php
@@ -267,17 +267,11 @@ public static function verify_http_signature( $request ) {
 			$headers['(request-target)'][0] = strtolower( $headers['request_method'][0] ) . ' ' . $headers['request_uri'][0];
 		}
 
-		if ( ! isset( $headers['signature'] ) ) {
-			return new WP_Error( 'activitypub_signature', __( 'Request not signed', 'activitypub' ), array( 'status' => 401 ) );
-		}
-
 		if ( array_key_exists( 'signature', $headers ) ) {
 			$signature_block = self::parse_signature_header( $headers['signature'][0] );
 		} elseif ( array_key_exists( 'authorization', $headers ) ) {
 			$signature_block = self::parse_signature_header( $headers['authorization'][0] );
-		}
-
-		if ( ! isset( $signature_block ) || ! $signature_block ) {
+		} else {
 			return new WP_Error( 'activitypub_signature', __( 'Incompatible request signature. keyId and signature are required', 'activitypub' ), array( 'status' => 401 ) );
 		}
 
diff --git a/includes/collection/class-actors.php b/includes/collection/class-actors.php
index df2e99918..d4dbd6ec5 100644
--- a/includes/collection/class-actors.php
+++ b/includes/collection/class-actors.php
@@ -76,6 +76,17 @@ public static function get_by_id( $user_id ) {
 	 * @return User|Blog|Application|WP_Error The Actor or WP_Error if user not found.
 	 */
 	public static function get_by_username( $username ) {
+		/**
+		 * Filter the username before we do anything else.
+		 *
+		 * @param null   $pre      The pre-existing value.
+		 * @param string $username The username.
+		 */
+		$pre = apply_filters( 'activitypub_pre_get_by_username', null, $username );
+		if ( null !== $pre ) {
+			return $pre;
+		}
+
 		// Check for blog user.
 		if ( Blog::get_default_username() === $username ) {
 			return new Blog();
@@ -110,7 +121,10 @@ public static function get_by_username( $username ) {
 		);
 
 		if ( $user->results ) {
-			return self::get_by_id( $user->results[0] );
+			$actor = self::get_by_id( $user->results[0] );
+			if ( ! \is_wp_error( $actor ) ) {
+				return $actor;
+			}
 		}
 
 		$username = str_replace( array( '*', '%' ), '', $username );
@@ -128,7 +142,10 @@ public static function get_by_username( $username ) {
 		);
 
 		if ( $user->results ) {
-			return self::get_by_id( $user->results[0] );
+			$actor = self::get_by_id( $user->results[0] );
+			if ( ! \is_wp_error( $actor ) ) {
+				return $actor;
+			}
 		}
 
 		return new WP_Error(
@@ -164,6 +181,9 @@ public static function get_by_resource( $uri ) {
 			$scheme = \esc_attr( $match[1] );
 		}
 
+		// @todo: handle old domain URIs here before we serve a new domain below when we shouldn't.
+		// Although maybe passing through to ::get_by_username() is enough?
+
 		switch ( $scheme ) {
 			// Check for http(s) URIs.
 			case 'http':
@@ -217,7 +237,7 @@ public static function get_by_resource( $uri ) {
 				$host       = normalize_host( \substr( \strrchr( $uri, '@' ), 1 ) );
 				$blog_host  = normalize_host( \wp_parse_url( \home_url( '/' ), \PHP_URL_HOST ) );
 
-				if ( $blog_host !== $host ) {
+				if ( $blog_host !== $host && get_option( 'activitypub_old_host' ) !== $host ) {
 					return new WP_Error(
 						'activitypub_wrong_host',
 						\__( 'Resource host does not match blog host', 'activitypub' ),
@@ -299,6 +319,43 @@ public static function get_collection() {
 		return $return;
 	}
 
+	/**
+	 * Get all active Actors including the Blog Actor.
+	 *
+	 * @return array The actor collection.
+	 */
+	public static function get_all() {
+		$return = array();
+
+		if ( ! is_user_type_disabled( 'user' ) ) {
+			$users = \get_users(
+				array(
+					'capability__in' => array( 'activitypub' ),
+				)
+			);
+
+			foreach ( $users as $user ) {
+				$actor = User::from_wp_user( $user->ID );
+
+				if ( \is_wp_error( $actor ) ) {
+					continue;
+				}
+
+				$return[] = $actor;
+			}
+		}
+
+		// Also include the blog actor if active.
+		if ( ! is_user_type_disabled( 'blog' ) ) {
+			$blog_actor = self::get_by_id( self::BLOG_USER_ID );
+			if ( ! \is_wp_error( $blog_actor ) ) {
+				$return[] = $blog_actor;
+			}
+		}
+
+		return $return;
+	}
+
 	/**
 	 * Returns the actor type based on the user ID.
 	 *
diff --git a/includes/functions.php b/includes/functions.php
index 09509bea6..d71f29995 100644
--- a/includes/functions.php
+++ b/includes/functions.php
@@ -134,7 +134,8 @@ function url_to_authorid( $url ) {
 	global $wp_rewrite;
 
 	// Check if url hase the same host.
-	if ( \wp_parse_url( \home_url(), \PHP_URL_HOST ) !== \wp_parse_url( $url, \PHP_URL_HOST ) ) {
+	$request_host = \wp_parse_url( $url, \PHP_URL_HOST );
+	if ( \wp_parse_url( \home_url(), \PHP_URL_HOST ) !== $request_host && get_option( 'activitypub_old_host' ) !== $request_host ) {
 		return null;
 	}
 
diff --git a/includes/model/class-blog.php b/includes/model/class-blog.php
index 23c95bcb9..e46e5b025 100644
--- a/includes/model/class-blog.php
+++ b/includes/model/class-blog.php
@@ -7,12 +7,11 @@
 
 namespace Activitypub\Model;
 
-use WP_Query;
-
-use Activitypub\Signature;
 use Activitypub\Activity\Actor;
 use Activitypub\Collection\Actors;
 use Activitypub\Collection\Extra_Fields;
+use Activitypub\Signature;
+use WP_Query;
 
 use function Activitypub\esc_hashtag;
 use function Activitypub\is_single_user;
@@ -92,6 +91,18 @@ class Blog extends Actor {
 	 */
 	protected $posting_restricted_to_mods;
 
+	/**
+	 * Constructor.
+	 */
+	public function __construct() {
+		/**
+		 * Fires when a model actor is constructed.
+		 *
+		 * @param Blog $this The Blog model.
+		 */
+		\do_action( 'activitypub_construct_model_actor', $this );
+	}
+
 	/**
 	 * Whether the User manually approves followers.
 	 *
@@ -116,6 +127,12 @@ public function get_discoverable() {
 	 * @return string The User ID.
 	 */
 	public function get_id() {
+		$id = parent::get_id();
+
+		if ( $id ) {
+			return $id;
+		}
+
 		$permalink = \get_option( 'activitypub_use_permalink_as_id_for_blog', false );
 
 		if ( $permalink ) {
@@ -576,7 +593,8 @@ public function get_also_known_as() {
 	 * @return string The movedTo.
 	 */
 	public function get_moved_to() {
-		// phpcs:ignore Universal.Operators.DisallowShortTernary.Found
-		return \get_option( 'activitypub_blog_user_moved_to' ) ?: null;
+		$moved_to = \get_option( 'activitypub_blog_user_moved_to' );
+
+		return $moved_to && $moved_to !== $this->get_id() ? $moved_to : null;
 	}
 }
diff --git a/includes/model/class-user.php b/includes/model/class-user.php
index c12fccafc..964c78677 100644
--- a/includes/model/class-user.php
+++ b/includes/model/class-user.php
@@ -7,10 +7,10 @@
 
 namespace Activitypub\Model;
 
-use WP_Error;
-use Activitypub\Signature;
 use Activitypub\Activity\Actor;
 use Activitypub\Collection\Extra_Fields;
+use Activitypub\Http;
+use Activitypub\Signature;
 
 use function Activitypub\is_blog_public;
 use function Activitypub\get_rest_url_by_path;
@@ -71,6 +71,24 @@ class User extends Actor {
 	 */
 	protected $webfinger;
 
+	/**
+	 * Constructor.
+	 *
+	 * @param int $user_id Optional. The WordPress user ID. Default null.
+	 */
+	public function __construct( $user_id = null ) {
+		if ( $user_id ) {
+			$this->_id = $user_id;
+
+			/**
+			 * Fires when a model actor is constructed.
+			 *
+			 * @param User $this The User object.
+			 */
+			\do_action( 'activitypub_construct_model_actor', $this );
+		}
+	}
+
 	/**
 	 * The type of the object.
 	 *
@@ -85,21 +103,18 @@ public function get_type() {
 	 *
 	 * @param int $user_id The user ID.
 	 *
-	 * @return WP_Error|User The User object or WP_Error if user not found.
+	 * @return \WP_Error|User The User object or \WP_Error if user not found.
 	 */
 	public static function from_wp_user( $user_id ) {
 		if ( ! user_can_activitypub( $user_id ) ) {
-			return new WP_Error(
+			return new \WP_Error(
 				'activitypub_user_not_found',
 				\__( 'User not found', 'activitypub' ),
 				array( 'status' => 404 )
 			);
 		}
 
-		$object      = new static();
-		$object->_id = $user_id;
-
-		return $object;
+		return new static( $user_id );
 	}
 
 	/**
@@ -108,6 +123,12 @@ public static function from_wp_user( $user_id ) {
 	 * @return string The user ID.
 	 */
 	public function get_id() {
+		$id = parent::get_id();
+
+		if ( $id ) {
+			return $id;
+		}
+
 		$permalink = \get_user_option( 'activitypub_use_permalink_as_id', $this->_id );
 
 		if ( '1' === $permalink ) {
@@ -367,7 +388,7 @@ public function get_indexable() {
 	 * Update the username.
 	 *
 	 * @param string $value The new value.
-	 * @return int|WP_Error The updated user ID or WP_Error on failure.
+	 * @return int|\WP_Error The updated user ID or \WP_Error on failure.
 	 */
 	public function update_name( $value ) {
 		$userdata = array(
@@ -446,7 +467,8 @@ public function get_also_known_as() {
 	 * @return string The movedTo.
 	 */
 	public function get_moved_to() {
-		// phpcs:ignore Universal.Operators.DisallowShortTernary.Found
-		return \get_user_option( 'activitypub_moved_to', $this->_id ) ?: null;
+		$moved_to = \get_user_option( 'activitypub_moved_to', $this->_id );
+
+		return $moved_to && $moved_to !== $this->get_id() ? $moved_to : null;
 	}
 }
diff --git a/tests/includes/class-test-move.php b/tests/includes/class-test-move.php
index 57ff882ee..a56ee23e0 100644
--- a/tests/includes/class-test-move.php
+++ b/tests/includes/class-test-move.php
@@ -8,12 +8,13 @@
 namespace Activitypub\Tests;
 
 use Activitypub\Collection\Actors;
-use Activitypub\Model\User;
+use Activitypub\Model\Blog;
+use Activitypub\Move;
 
 /**
  * Test class for Activitypub Move.
  *
- * @coversDefaultClass \Activitypub\Move
+ * @coversDefaultClass Move
  */
 class Test_Move extends \WP_UnitTestCase {
 
@@ -40,7 +41,7 @@ public function test_account_with_valid_input() {
 		$from = Actors::get_by_id( self::$user_id )->get_id();
 		$to   = 'https://newsite.com/user/1';
 
-		\Activitypub\Move::externally( $from, $to );
+		Move::externally( $from, $to );
 
 		$moved_to = Actors::get_by_id( self::$user_id )->get_moved_to();
 		$this->assertEquals( $to, $moved_to );
@@ -55,7 +56,7 @@ public function test_account_with_valid_input() {
 	 * @covers ::account
 	 */
 	public function test_account_with_invalid_user() {
-		$result = \Activitypub\Move::externally(
+		$result = Move::externally(
 			'https://example.com/nonexistent/user',
 			'https://newsite.com/user/999'
 		);
@@ -78,7 +79,7 @@ public function test_account_with_invalid_target() {
 		};
 		\add_filter( 'pre_http_request', $filter );
 
-		$result = \Activitypub\Move::externally( $from, $to );
+		$result = Move::externally( $from, $to );
 
 		$this->assertWPError( $result );
 		$this->assertEquals( 'http_request_failed', $result->get_error_code() );
@@ -105,7 +106,7 @@ public function test_account_with_duplicate_moves() {
 		};
 		\add_filter( 'pre_http_request', $filter );
 
-		\Activitypub\Move::externally( $from, $to );
+		Move::externally( $from, $to );
 
 		$moved_to = Actors::get_by_id( self::$user_id )->get_moved_to();
 		$this->assertEquals( $to, $moved_to );
@@ -125,7 +126,7 @@ public function test_account_with_blog_author_as_actor() {
 		$from = Actors::get_by_id( Actors::BLOG_USER_ID )->get_id();
 		$to   = 'https://newsite.com/user/0';
 
-		\Activitypub\Move::externally( $from, $to );
+		Move::externally( $from, $to );
 
 		$moved_to = Actors::get_by_id( Actors::BLOG_USER_ID )->get_moved_to();
 		$this->assertEquals( $to, $moved_to );
@@ -142,13 +143,14 @@ public function test_internally_with_valid_input() {
 		$from = get_author_posts_url( self::$user_id );
 		$to   = Actors::get_by_id( self::$user_id )->get_id();
 
-		\Activitypub\Move::internally( $from, $to );
+		Move::internally( $from, $to );
 
 		// Clear cache.
 		wp_cache_delete( self::$user_id, 'users' );
 
+		// Updated user should not have moved_to set.
 		$moved_to = Actors::get_by_id( self::$user_id )->get_moved_to();
-		$this->assertEquals( $to, $moved_to );
+		$this->assertNull( $moved_to );
 
 		$also_known_as = Actors::get_by_id( self::$user_id )->get_also_known_as();
 		$this->assertContains( $from, $also_known_as );
@@ -164,7 +166,7 @@ public function test_internally_activity_object_properties() {
 		$to   = Actors::get_by_id( self::$user_id )->get_id();
 
 		// Call the method and get the outbox item ID.
-		$outbox_id = \Activitypub\Move::internally( $from, $to );
+		$outbox_id = Move::internally( $from, $to );
 
 		// Verify we got a valid outbox ID.
 		$this->assertIsInt( $outbox_id );
@@ -187,4 +189,43 @@ public function test_internally_activity_object_properties() {
 		$this->assertEquals( $from, $activity->origin );
 		$this->assertEquals( $to, $activity->target );
 	}
+
+	/**
+	 * Test the change_domain() method with valid input.
+	 *
+	 * @covers ::change_domain
+	 */
+	public function test_change_domain_with_valid_input() {
+		// Enable blog actor.
+		\update_option( 'activitypub_actor_mode', ACTIVITYPUB_ACTOR_AND_BLOG_MODE );
+
+		$old_domain = home_url();
+		$new_domain = 'http://newdomain.com';
+		\remove_filter( 'option_home', '_config_wp_home' );
+		\update_option( 'home', $new_domain );
+
+		// Run the domain change.
+		$results = Move::change_domain( $old_domain, $new_domain );
+
+		// Verify the results.
+		$this->assertIsArray( $results );
+
+		// Check that each result has the expected structure.
+		$result      = reset( $results );
+		$outbox_item = json_decode( get_post_field( 'post_content', $result['result'] ) );
+
+		$this->assertSame( $outbox_item->target, $result['actor'] );
+		$this->assertStringStartsWith( $new_domain, $outbox_item->target );
+
+		// Verify the old host was stored.
+		$this->assertEquals( 'example.org', \get_option( 'activitypub_old_host' ) );
+
+		// Clean up.
+		\delete_option( 'activitypub_old_host' );
+		\delete_option( 'activitypub_blog_user_old_host_data' );
+		\delete_option( 'activitypub_actor_mode' );
+		\update_option( 'home', $old_domain );
+		\add_filter( 'option_home', '_config_wp_home' );
+		\delete_user_option( self::$user_id, 'activitypub_old_host_data' );
+	}
 }
diff --git a/tests/includes/model/class-test-blog.php b/tests/includes/model/class-test-blog.php
new file mode 100644
index 000000000..eb154afa8
--- /dev/null
+++ b/tests/includes/model/class-test-blog.php
@@ -0,0 +1,72 @@
+<?php
+/**
+ * Test file for Activitypub Blog Model.
+ *
+ * @package Activitypub
+ */
+
+namespace Activitypub\Tests\Model;
+
+use Activitypub\Model\Blog;
+use Activitypub\Move;
+
+/**
+ * Test class for Activitypub Blog Model.
+ *
+ * @coversDefaultClass Blog
+ */
+class Test_Blog extends \WP_UnitTestCase {
+
+	/**
+	 * Set up before class.
+	 */
+	public static function set_up_before_class() {
+		parent::set_up_before_class();
+
+		// Enable blog actor.
+		\update_option( 'activitypub_actor_mode', ACTIVITYPUB_ACTOR_AND_BLOG_MODE );
+	}
+
+	/**
+	 * Tear down after class.
+	 */
+	public static function tear_down_after_class() {
+		// Disable blog actor.
+		\delete_option( 'activitypub_actor_mode' );
+
+		parent::tear_down_after_class();
+	}
+
+	/**
+	 * Test the Blog constructor.
+	 *
+	 * @covers ::__construct
+	 */
+	public function test___construct() {
+		$old_domain = home_url( '/' );
+		$new_domain = 'http://newdomain.com';
+		\remove_filter( 'option_home', '_config_wp_home' );
+
+		\add_filter( 'update_option_home', array( Move::class, 'change_domain' ), 10, 2 );
+		\update_option( 'home', $new_domain );
+		\remove_filter( 'update_option_home', array( Move::class, 'change_domain' ) );
+
+		// New domain is set.
+		$this->assertSame( 'http://newdomain.com/?author=0', ( new Blog() )->get_id() );
+
+		// Set up the old host.
+		$_SERVER['HTTP_HOST'] = \wp_parse_url( $old_domain, PHP_URL_HOST );
+
+		// Blog now returns old blog actor.
+		\add_action( 'activitypub_construct_model_actor', array( Move::class, 'maybe_initiate_old_user' ) );
+		$blog = ( new Blog() )->to_array();
+		$this->assertSame( add_query_arg( 'author', 0, $old_domain ), $blog['id'] );
+		\remove_action( 'activitypub_construct_model_actor', array( Move::class, 'maybe_initiate_old_user' ) );
+
+		// Clean up.
+		\delete_option( 'activitypub_old_host' );
+		\delete_option( 'activitypub_blog_user_old_host_data' );
+		\update_option( 'home', $old_domain );
+		\add_filter( 'option_home', '_config_wp_home' );
+	}
+}
diff --git a/tests/includes/model/class-test-user.php b/tests/includes/model/class-test-user.php
index fd56d1a07..a0bd6e728 100644
--- a/tests/includes/model/class-test-user.php
+++ b/tests/includes/model/class-test-user.php
@@ -8,14 +8,48 @@
 namespace Activitypub\Tests\Model;
 
 use Activitypub\Model\User;
+use Activitypub\Move;
 
 /**
  * Test class for Activitypub User.
  *
- * @coversDefaultClass \Activitypub\Model\User
+ * @coversDefaultClass User
  */
 class Test_User extends \WP_UnitTestCase {
 
+	/**
+	 * Test the Blog constructor.
+	 *
+	 * @covers ::__construct
+	 */
+	public function test___construct() {
+		$old_domain = home_url( '/' );
+		$new_domain = 'http://newdomain.com';
+		\remove_filter( 'option_home', '_config_wp_home' );
+
+		\add_filter( 'update_option_home', array( Move::class, 'change_domain' ), 10, 2 );
+		\update_option( 'home', $new_domain );
+		\remove_filter( 'update_option_home', array( Move::class, 'change_domain' ) );
+
+		// New domain is set.
+		$this->assertSame( 'http://newdomain.com/?author=1', ( new User( 1 ) )->get_id() );
+
+		// Set up the old host.
+		$_SERVER['HTTP_HOST'] = \wp_parse_url( $old_domain, PHP_URL_HOST );
+
+		// User now returns old user actor.
+		\add_action( 'activitypub_construct_model_actor', array( Move::class, 'maybe_initiate_old_user' ) );
+		$user = ( new User( 1 ) )->to_array();
+		$this->assertSame( add_query_arg( 'author', 1, $old_domain ), $user['id'] );
+		\remove_action( 'activitypub_construct_model_actor', array( Move::class, 'maybe_initiate_old_user' ) );
+
+		// Clean up.
+		\delete_option( 'activitypub_old_host' );
+		\delete_option( 'activitypub_blog_user_old_host_data' );
+		\update_option( 'home', $old_domain );
+		\add_filter( 'option_home', '_config_wp_home' );
+	}
+
 	/**
 	 * Test the activitypub capability.
 	 */